The subject matter disclosed herein relates generally to a system for connecting power between devices and, more specifically, to a system for electrically connecting a shared direct current (DC) bus between multiple power converters.
As is known to those skilled in the art, power converters are utilized in numerous applications to convert power from one form to another. Power converters may, for example, convert power generated by an alternating current (AC) power supply to DC power or power generated by a DC power supply to AC power. Power converters are also utilized to convert DC power at a first voltage potential to a second voltage potential or to supply AC voltage having a variable amplitude and variable frequency.
One exemplary use of power converters is to provide voltage for the control of an AC motor. An inverter, for example, converts power from a DC source to an AC output connected to the motor. The AC output has a varying amplitude and/or varying frequency to control the torque and/or speed at which the motor operates. The DC source is commonly referred to as a DC bus. The DC bus, in turn, typically receives power from a second power converter. If the DC bus is receiving power from an energy storage device, such as a battery, the power converter may be a DC-to-DC converter which converts power having a first voltage potential present on the energy storage device to a second voltage potential present on the DC bus. If the DC bus is receiving energy from an AC power source, such as the utility grid, the power converter may be an AC-to-DC converter which converts the AC voltage to a DC voltage on the DC bus.
It certain applications, such as a process line or a machining center, there may be multiple motors, each controlling a different axis of motion, which receive their power from the utility grid. It may be advantageous to provide a single AC-to-DC converter, or rectifier, having sufficient power rating to provide power for each motor converting the AC power from the utility grid to the DC power on the DC bus. Each motor may then have an associated inverter connected to the shared DC bus and be configured to provide AC power to the motor to control operation of the motor. In such a configuration, it is necessary to connect each of the inverters to the DC bus in order for them to receive power from the DC bus.
Presently, the rectifier and each inverter may be mounted proximate to each other in a control cabinet. Each of the power converters may include a set of terminals having, for example, a screw clamp, configured to secure an appropriate gauge electrical conductor, or a bolt hole, through which a bolt may secure a lug which is, in turn, crimped to the electrical conductor. The screw or bolt mechanical connection is desired due to the amplitude of voltage and/or current that may be present on the DC bus. For example, a 230 VAC motor requires a DC voltage potential of about 325 VDC or more to be present on the DC bus and the current may be tens or hundreds of amps. The electrical conductor may be an insulated wire or cable depending on the power requirements of the application. Optionally, solid conductive bars, such as copper bars, may be stamped or manufactured that are secured between power converters.
However, such systems have not been fully met without incurring various disadvantages. Installation and maintenance of the drives requires securing the electrical conductors to the power converters. If more than two power converters are sharing the DC bus, the technician must be trained to properly chain the converters in series and for each converter located in series between two other converters, multiple conductors need to be secured to the power converter.
Thus, it would be desirable to provide a system for connecting power converters sharing a DC bus that provides for easier installation and maintenance.